Acrylic fiber is an important synthetic fiber material and is the basic raw material for the textile industry. China is a large producer of acrylic fiber in the world and has many large-scale enterprises for producing acrylic fiber. Wastewater produced from acrylic fiber production is a typical non-biodegradable and toxic organic industrial wastewater, which contains varieties of toxic organic compounds such as acrylonitrile, DMAC and DMF. It also contains high concentrations of non-biodegradable organics. The traditional treatment process is difficult to meet standards, so it has always been a challenge for treating thus produced wastewater in the industrial wastewater treatment field. China's Integrated Wastewater Discharge Standard (GB8978-1996) has modified the COD standard value for special petrochemical plants including acrylonitrile-acrylic fiber plants. In China's newly issued “Petrochemical Industry Pollutant Discharge Standard” (GB 31571-2015), the COD emission limits for special petrochemical plants including acrylonitrile-acrylic fiber plants are 40 mg/L higher than that of other chemical production facilities.
In addition to the non-biodegradable organic additives added during the production process, the non-biodegradable organics in the wastewater yielded in the production of acrylic fiber include high-molecular-weight polymers (above 10 kDa) and low-molecular-weight polymers (below 10 kDa) which are produced during the polymerization and enter the wastewater. High-molecular-weight polymers are products that are lost to the wastewater in the production of acrylic fibers and have a recovery value. Low-molecular-weight polymers are difficult to remove using conventional techniques. The current technologies mostly focus on the treatment of the final discharge for enhancing the removal of non-biodegradable pollutants, while there is lack of a technology aiming to reduce the pollutants by means of optimizing the process for producing acrylic fibers and reducing the pollutants in the wastewater discharged in each procedure of the process.